Whistle ban or Pre-Rule Quiet Zone
A whistle ban is a local prohibition of the sounding of locomotive horns at specific highway-rail grade crossings. Historically, whistle bans were established by local ordinance or through agreements with specific railroads in accordance with existing state law. At whistle ban crossings, no specific safety improvements have been made to compensate for the absence of the audible warning. Pre-Rule Quiet Zones established under this rule may only consist of Whistle Ban crossings that were in effect on October 9, 1996 and on December 18, 2003.
Source: Federal Railroad Administration